If you mean connect up all the cables to allow 5.1 over analogue, then yep, that would work.
A lot of amps will require you to change from Optical to Analogue though. I've never seen one do it automatically (I'm not saying they don't exist though
)
As for using prologic2 + digital, its much better to hook all the analogue outputs direct from the card as opposed to using just one and getting the amp to do PL2 on it.
Sure, PL2 is nice, but what's the point in using it if you can take 5.1 separate, discrete, true channels from the card as opposed to taking what essentially still is a stereo source and getting the amp to use PL2 to make it into "5.1"?
Its never going to be on the same level as true 5.1 generated from the card.
Remember, Creative cards can happily
decode Dolby Digital. All you would be doing is going Dolby Digital -> Stereo -> PL2 off the Stereo source to make it back into "5.1". Thats a heck of a lot of conversion and plenty of quality loss
It makes 100x more sense to go Dolby Digital -> Decode to 5.1 -> Amp 5.1 analogue
You keep the orignal channels intact that way